This study investigated the antinociceptive effects of the methanolic extract of the stem wood ofMicrodermis puberula (Hook. F. Ex. Planch) in Swiss albino mice of either sex with weights ranging from 17 to 25 g. Acetylsalicylic acid and morphine were used as standards for the antinociceptive tests while distilled water was used as control. Acetic acid - induced mouse writhing reflex test and hot plate test were used to determine peripheral and central pain inhibition respectively, using five groups of five animals for each model. The extract was administered in three dosages: 600, 1200 and 2400 mg/kg orally. Acetylsalicylic acid was administered at 100 mg/kg p.o., morphine at 10 mg/kg intraperitoneally and distilled water at 1 ml/kg p.o. Results showed that the extract of. Microdermis puberula, at 1200 and 2400 mg/kg significantly inhibited peripheral pain, compared with acetylsalicylic acid (p<0.05). The extract of Microdermis puberula, at a dose of 2400 mg/kg inhibited pain by increasing the pain threshold in the hot plate test 58.83%. These, therefore, suggest that the methanolic extract ofMicrodermis puberula possesses mild antinociceptive property. The phytochemical analyses of the extract showed the presence of flavonoids, saponins and cardiac glycosides. Results from the LD50 determination showed that a dose of 1412.5 mg/kg i.p. produced 50% death in mice.
Key words: Antinociceptive, Microdemis puberula, phytochemical analysis, LD50, acetylsalicylic acid.
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